[abawany]

(I promise, I am not shilling) Meetup (meetup.com) lets you make a group for I think $20/month (group participants can contribute to help the organizer) and is perfect for organizing events, sending calendar invites, providing a group forum and mailing list. I have been using it for about 10 years to keep up with local tech groups and it works great.

[Larrikin]

I love meetup and have found it extremely useful in a new city to try and meet people with similar hobbies. But I've also found there are basically two types. The people who are truly passionate about a hobby and are willing to take losses occasionally and the groups that are sponsored for an obvious reason. In Japan, where I discovered the site, there were lots of groups that just wanted to get native English speakers so they members didn't need to pay for English classes. In America most of the tech events are simply put on by companies who are looking to hire. Often times the events are still worth it and enjoyable, but it's definitely disappointing if you go to one and don't realize the underlying reason for the group existing. I've found the ones put on by the passionate people to be the most worthwhile and worth the more expensive dues.